High speed downlink packet access (HSDPA) technology is a new technology introduced by 3GPP (3rd Generation Partnership Project) in Release 5, which can improve a data transmission rate in a downlink direction of the packet service and can improve a frequency utilization ratio of the system. According to the HSDPA technology, multiple users share code channel resources and a higher rate is allocated to a UE (user equipment) with a good channel environment and a lower rate is allocated to a UE with a bad channel environment by the AMC (Adaptive Modulation and Coding)) and HARQ (Hybrid Automatic Repeat Request) technologies. The HSDPA technology is also adaptable to three different modes of WCDMA FDD (Wideband Code Division Multiple Access-Frequency Division Duplex), UTRA TDD (Universal Telecommunication Radio Access Time Division Duplex) and TD-SCDMA (Time Division-Synchronous Code Division Multiple Access).
For the UE working at a single frequency, when the data transmission is performed with the HSDPA technology, the HS-DSCH (High Speed Downlink Shared Channel) is used to carry high layer data and the data on the HS-DSCH are mapped to a HS-PDSCH (High Speed Physical Downlink Shared Channel) to be transmitted after being coded and interleaved; the UE interacts with the network about the control information through a HS-SCCH (High Speed Shared Control Channel) and a HS-SICH (High Speed Shared Information Channel)/HS-DPCCH (High Speed Dedicated Physical Control Channel). The HS-SCCH corresponds to the HS-SICH one by one and a plurality of pairs of HS-SCCH/HS-SICH can be allocated in one cell but one UE at most needs to concurrently monitor 4 HS-SCCHs.
During the communication process, in the TDD system, when the network side has data to be transmitted to some UE at some time through a scheduling algorithm, the network side selects one HS-SCCH from a set of HS-SCCHs allocated to the UE and transmits information related to the data transmitted to the UE to the UE, wherein the information generally comprises number of code channels of HS-PDSCH to be received, number of time slots, indicator of data length, adopted modulation mode, RV version and indicator flag of new data etc. and the UE receives and processes the HS-PDSCH according to the control information of the HS-SCCH, replies the ACK/NACK and CQI (channel quality indicator) to the network side through the HS-SICH and the network side controls the subsequent transmission of data to the UE according to the information.
FIG. 1 illustrates an interaction flow of data transmission according to the HSDPA technology between the UE and the network side at the single frequency in a conventional TDD system.
1. A RNC (Radio Network Controller) configures related resources of HS-PDSCH/HS-SCCH/HS-SICH (comprising information of code channel, time slot, midamble etc.) for a Node B through a physical shared channel reconfiguration request according to network planning;
2. When a UE supporting the HSDPA accesses the network, it reports a service request and its capability to the network side;
3. When the RNC at the network side determines the access is allowed according to the requested service type and the capability of the UE, it transmits the capability of the UE to the Node B and requests the Node B to allocate resources for the UE, comprising a set of HS-SCCH/HS-SICH to be monitored by the UE;
4. The Node B allocates related shared resources for the UE, such as the set of HS-SCCH/HS-SICH, and transmits the information to the RNC;
5. The RNC transmits related shared resources allocated for the UE to the UE;
6. During the realtime communication, when the Node B transmits data to the UE at some time according to the scheduling algorithm, it selects one HS-SCCH from the set of the HS-SCCH/HS-SICH monitored by the UE to indicate the related control information of the HS-PDSCH carrying data, transmits the coded and multiplexed HS-SCCH to the UE and maps the processed data to the corresponding HS-PDSCH according to the timing relation and transmits to the UE;
7. The UE monitors the HS-SCCHs in the monitored set of HS-SCCH/HS-SICH and when it receives the HS-SCCH and after the decoding processing, it determines the HS-PDSCH data to be received, receives the HS-PDSCH data according to the control information transmitted on the HS-SCCH, and transmits a reply message (such as NACK/ACK) through the HS-SICH corresponding to the HS-SCCH to the Node B according to the decoding result (when the decoding data is right, ACK is replied, when the decoding data is wrong, NACK is replied; CQI is the channel quality indicator).
The current HSDPA technology operates on a single frequency cell and the UE supporting the single frequency. The network side interchanges the control information with the UE through the shared control channel and the network side notifies the UE through the HS-SCCH about whether to receive the subsequent HS-PDSCH, length of data and modulation mode on the HS-PDSCH, and redundancy version etc.; the UE replies the NACK/ACK and the CQI to the network side through the HS-SICH (for the TDD system) or the HS-DPCCH (for the FDD system). However, for the UE supporting multiple frequencies, when it operates in a multi-frequency cell, the data can be concurrently transmitted at multiple frequencies, but the UE can not be controlled to receive data at multiple frequencies.